Comparison of ocular aberrations measured by a Fourier-based Hartmann-Shack and Zernike-based Tscherning aberrometer before and after laser in situ keratomileusis

Corneal Higher-Order Aberrations Measurements: Precision of SD-OCT/Placido Topography and Comparison with a Scheimpflug/Placido Topography in Eyes After Small-Incision Lenticule Extraction

INTRODUCTION

The aim of this study was to evaluate the measurements of corneal higher-order aberrations (HOAs) obtained by a new anterior segment optical coherence tomography (OCT) technique combined with a Placido topographer (the MS-39 device) in eyes with prior small-incision lenticule extraction (SMILE) and compare them to the measurements obtained by a Scheimpflug camera combined with a Placido topographer (the Sirius device).

METHODS

A total of 56 eyes (56 patients) were included in this prospective study. Corneal aberrations were analyzed for the anterior, posterior, and total cornea surfaces. Within-subject standard deviation (S_w), test-retest repeatability (TRT), and intraclass correlation coefficient (ICC) were used to assess the intraobserver repeatability and interobserver reproducibility. The differences were evaluated by paired t-test. Bland-Altman plots and 95% limits of agreement (95% LoA) were used to evaluate the agreement.

RESULTS

High repeatability was observed for anterior and total corneal parameters, with S_w value < 0.07, TRT ≤ 0.16, and ICCs > 0.893, but not trefoil. For the posterior corneal parameters, ICCs varied from 0.088 to 0.966. Regarding interobserver reproducibility, all S_w values were ≤ 0.04 and TRT ≤ 0.11. ICCs ranged from 0.846 to 0.989, from 0.432 to 0.972, and from 0.798 to 0.985 for the anterior, total, and posterior corneal aberrations parameters, respectively. The mean difference in all aberrations was ≤ 0.05 μm. All parameters showed a narrow 95% LoA.

CONCLUSION

The MS-39 device achieved high precision in both anterior and total corneal measurements; the precision of posterior corneal higher-order RMS, astigmatism II, coma, and trefoil was lower. The two technologies used by the MS-39 and Sirius devices can be used interchangeably for measuring corneal HOAs after SMILE.

Bias of near-infrared light in evaluation of patients implanted with multifocal intraocular lenses

PURPOSE

To compare visual quality between subjective tests and optical devices using near-infrared (NIR) light in patients implanted with monofocal, multifocal and enlarged depth-of-focus (EDoF) intraocular lenses (IOLs).

METHODS

Cross-sectional study enrolling patients aged between 55 and 75 (axial length between 22 and 25 mm) bilaterally implanted with Tecnis IOLs (Johnson & Johnson) four months previously: 40 patients (80 eyes) with monofocal ZCB00, 41 patients (82 eyes) with bifocal diffractive ZMB00 and 48 patients (96 eyes) with EDoF Symfony. They were examined using subjective and objective tests. The subjective tests comprised visual acuity (VA) with ETDRS charts, contrast sensitivity (CS) with Pelli-Robson and CSV-1000E tests, and clear vision range (CVR). The objective tests using NIR light were performed with the KR-1 W wavefront analyzer and the OQAS.

RESULTS

In the subjective tests, the monofocal group achieved the best outcomes in some of the VA and CS sections, while the bifocal group obtained the worst outcomes in some of the CS sections. In the objective tests, the bifocal group achieved the best results for VA and CS. Discrepancies between pseudoaccommodation range and CVR were found in the bifocal and EDoF groups.

CONCLUSIONS

Assessment of visual quality using NIR light implies greater bias for diffractive lenses than for EDoF lenses. This bias may be even greater with devices using longer light wavelengths or Hartmann-Shack technology. The difference in wavelength between NIR and visible light leads to dimming of near-vision focus and magnification of distance focus.

Comparative analysis of the efficacy of astigmatic correction after wavefront-guided and wavefront-optimized LASIK in low and moderate myopic eyes

AIM

To evaluate and compare the efficacy of the astigmatic correction achieved with laser in situ keratomileusis (LASIK) in eyes with myopic astigmatism using wavefront-guided (WFG) and wavefront-optimized (WFO) ablation profiles.

METHODS

Prospective study included 221 eyes undergoing LASIK: 99 and 122 eyes with low and moderate myopic astigmatism (low and moderate myopia groups). Two subgroups were differentiated in each group according to the ablation profile: WFG subgroup, 109 eyes (45/64, low/moderate myopia groups) treated using the Advanced CustomVue platform (Abbott Medical Optics Inc.), and WFO subgroup, 112 eyes (54/58, low/moderate myopia groups) treated using the EX-500 platform (Alcon). Clinical outcomes were evaluated during a 6-month follow-up, including a vector analysis of astigmatic changes.

RESULTS

Significantly better postoperative uncorrected visual acuity and efficacy index was found in the WFG subgroups of each group (P≤0.041). Postoperative spherical equivalent and cylinder were significantly higher in WFO subgroups (P≤0.003). In moderate myopia group, a higher percentage of eyes with a postoperative cylinder ≤0.25 D was found in the WFG subgroup (90.6% vs 65.5%, P=0.002). In low and moderate myopia groups, the difference vector was significantly higher in the WFO subgroup compared to WFG (P<0.001). In moderate myopia group, the magnitude (P=0.008) and angle of error (P<0.001) were also significantly higher in the WFO subgroup. Significantly less induction of high order aberrations were found with WFG treatments in both low and moderate myopia groups (P≤0.006).

CONCLUSION

A more efficacious correction of myopic astigmatism providing a better visual outcome is achieved with WFG LASIK compared to WFO LASIK.